RF ablation probes with tine valves

ABSTRACT

A tissue ablation probe is provided. The tissue ablation probe comprises an elongated shaft, at least one electrode tine carried by the elongated shaft, at least one tine exit from which the electrode tine(s) can be deployed from the elongated shaft and retracted within the elongated shaft, and a sheath covering the electrode tine exit(s). The sheath may, e.g., line an exterior surface of the elongated shaft or an interior surface of the elongated shaft. The sheath has at least one tine valve (e.g., a slit) positioned over the electrode tine exit(s) and configured to open when the electrode tine is deployed and to close when the electrode tine(s) is retracted. In one embodiment, the tine valve(s) is configured to open in response to pressure exerted during deployment of the electrode tine(s). In another embodiment, the tine valve(s) is configured to hinder the entry of biological material within the elongated shaft. In one embodiment, the sheath is pliable, such that the tine valve(s) can more easily hinder the entry of the biological material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/029,863, filed Feb. 17, 2011, now issued as U.S. Pat. No. 8,409,193,which is a continuation of U.S. application Ser. No. 11/323,941 filed onDec. 29, 2005, now issued as U.S. Pat. No. 7,896,874, the disclosures ofwhich are hereby incorporated by reference.

FIELD OF THE INVENTION

The field of the invention relates generally to the structure and use ofradio frequency (RF) electrosurgical probes for the treatment of tissue.

BACKGROUND OF THE INVENTION

In oncology, cancer treatment is often performed using radio frequency(RF) ablation techniques. Conventional ablation techniques use an arrayof RF needles or tines (“tine array”), which may be configured to deployin a pre-determined shape or pattern for transferring RF energy intosurrounding tissue. For example, in an undeployed state, tines areinserted into a target area while housed within the lumen of a cannula.An undeployed tine array enclosed within a cannula may be placed byinserting the cannula through bone and tissue into a target area. Onceinserted, the electrode tine array may be deployed by forcing theelectrode tines out of a cannula and into the surrounding target tissue.After deployment, RF energy may be transmitted from the electrode tinearray to ablate the target tissue, causing heating and eventual necrosisof cancerous or malignant tissue. RF ablation occurs when a highfrequency alternating current flows from one electrode to another,completing a current path, causing ionic agitation. Ionic agitationoccurs around an active electrode as a result of frictional heating inthe tissue surrounding the electrode tines (e.g., electrodes, RF needleprobes, and the like) on an array, leading to cell death and necrosis.After ablating the target tissue, the electrode tine array is thenretracted into the cannula.

A need continues for lower profile (smaller gauge) RF probes with largerelectrode arrays. In designing for these characteristics, everydiminutive amount of space inside the cannula of the RF probe must beutilized. As a result, an electrode array assembly must hold extremelytight clearances and tolerances in concert with the inner diameter ofthe cannula. Some problems associated with conventional ablationtechniques are associated with the deployment of tine arrays. Inparticular, biological material (e.g., tissue, coagulated blood, and thelike) can enter the lumen of a cannula during deployment or retraction.If blood and tissue enters the cannula, mechanical interference (i.e.,blockage, jamming, and the like) may result when the electrode tinearray is retracted or deployed again. When retracting the electrode tinearray, necrosed tissue and blood resulting from the ablation may adhereto the RF needle probes, causing a mechanical interference.

There, thus, remains a need to minimize the entry of biological materialinto an RF ablation cannula during deployment and/or retraction ofelectrode tines.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present inventions, a tissueablation probe is provided. The tissue ablation probe comprises anelongated shaft, at least one electrode tine carried by the elongatedshaft, at least one tine exit from which the electrode tine(s) can bedeployed from the elongated shaft and retracted within the elongatedshaft, and a sheath covering the electrode tine exit(s). The sheath may,e.g., line an exterior surface of the elongated shaft or an interiorsurface of the elongated shaft. The sheath has at least one pre-formedtine valve (e.g., a slit) positioned over the electrode tine exit(s) andconfigured to open when the electrode tine is deployed and to close whenthe electrode tine(s) is retracted. In one embodiment, the tine valve(s)is configured to open in response to pressure exerted during deploymentof the electrode tine(s). In another embodiment, the tine valve(s) isconfigured to hinder the entry of biological material within theelongated shaft. In one embodiment, the sheath is pliable, such that thetine valve(s) can more easily hinder the entry of the biologicalmaterial.

In accordance with a second aspect of the present inventions, anothertissue ablation probe is provided. The tissue ablation probe comprisesan elongated shaft, at least one electrode tine carried by the elongatedshaft, at least one tine exit from which the electrode tine(s) can bedeployed from the elongated shaft and retracted within the elongatedshaft, and a sheath covering the electrode tine exit(s). The sheath may,e.g., line an exterior surface of the elongated shaft or an interiorsurface of the elongated shaft. The sheath has at least one tine valvepositioned over the electrode tine exit(s) and configured to seal overthe electrode tine when deployed to hinder the entry of biologicalmaterial within the elongated shaft. The tine valve(s) may be preformedin the sheath, or alternatively, can be configured to be created uponpuncturing of the sheath via deployment of the of electrode tine(s).

The sheath is pliable, such that the tine valve(s) can more easily sealover the electrode tine(s) when deployed and close when the electrodetine(s) are retracted. In one embodiment, the tine valve(s) isconfigured to close in response to the retraction of the at least oneelectrode tine into the elongated shaft.

In accordance with a third aspect of the present inventions, stillanother tissue ablation probe is provided. The tissue ablation probecomprises an elongated shaft, at least one electrode tine carried by theelongated shaft, at least one tine exit from which the electrode tine(s)can be deployed from the elongated shaft and retracted within theelongated shaft, and a sheath covering the electrode tine exit(s). Thesheath may, e.g., line an exterior surface of the elongated shaft or aninterior surface of the elongated shaft. The sheath is configured toseal over the electrode tine when the electrode tine traverses thesheath to hinder the entry of biological material within the elongatedshaft. The sheath is pliable, such that sheath can more easily seal overthe electrode tine(s) when deployed. In an optional embodiment, thesheath remains sealed in response to the retraction of the electrodetine(s) into the elongated shaft. In performing the sealing function,the sheath may have at least one pre-formed tine valve that seals overthe at least one electrode tine when the electrode tine(s) traverses thesheath, or alternatively, may be configured to puncture when theelectrode tine(s) traverses the sheath to seal over the electrodetine(s).

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferredembodiment(s) of the invention, in which similar elements are referredto by common reference numerals. In order to better appreciate theadvantages and objects of the invention, reference should be made to theaccompanying drawings that illustrate the preferred embodiment(s). Thedrawings, however, depict the embodiment(s) of the invention, and shouldnot be taken as limiting its scope. With this caveat, the embodiment(s)of the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 is a plan view of one embodiment of a tissue ablation probeconstructed in accordance with the present inventions, particularlyshowing a sheath lining an exterior surface of a cannula with closedtine valves and electrode tines retracted within the cannula;

FIG. 2 is a cross-sectional view of the tissue ablation probe of FIG. 1,taken along the line 2-2;

FIG. 3 is a cross-sectional view of the tissue ablation probe of FIG. 1,particularly showing the tine valves opened;

FIG. 4 is a plan view of the tissue ablation probe of FIG. 1,particularly showing the electrode tines deployed from the cannula;

FIG. 5 is a plan view of the tissue ablation probe of FIG. 1,particularly showing a sheath lining an interior surface of the cannula;

FIG. 6 is a plan view of the tissue ablation probe of FIG. 1,particularly showing the sheath lining the exterior surface along only aportion of the cannula; and

FIG. 7 is a plan view of the tissue ablation probe of FIG. 1,particularly showing offset tine valves.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The following described embodiments utilize tine valves that are used toprevent mechanical interferences that may interfere with the deploymentor retraction of a tine array. Tine valves secure tine exits, acting asa barrier to prevent or otherwise minimize, filter, reduce, materialfrom entering a cannula during deployment and retraction of a tinearray. A covering material (i.e., sheath) may be used to cover theelectrode tine exits, enabling the tine valves to open or close when atine array is deployed or retracted. The tine valves may be preformedwithin the sheath or can be made when the tine array punctures thesheath. The sheath seals over the electrode tine exits as the electrodetine array is fully retracted into a cannula and opens fully whendeploying the electrode tine array. During either retraction ordeployment, the sheath also forms a seal and contact with the individualtines of the electrode tine array. The sheath may remove (or minimize,reduce) any material adhering to the electrode tines as the electrodetine array is retracted or prevent (or minimize, reduce) material fromentering the cannula. The tine valves prevent (or minimize, reduce) anymechanical interference resulting from material (e.g., necrosed tissueor blood) adhering to individual tines when a tine array is retracted ordeployed. Several examples are provided below, but are not limited toonly the described implementations.

Referring to FIGS. 1-4, an exemplary ablation probe 100 constructed inaccordance with one embodiment of the present inventions is described.The ablation probe 100 comprises an elongated cannula 102 and an arrayof electrode tines 104 (shown in FIGS. 2 and 4) configured to beselectively deployed out of, and retracted within, the cannula 102 viatine exits 106 formed in the side of the cannula 102. In the illustratedembodiment, the elongated cannula 102 is rigid, so that it can bepercutaneously introduced through tissue. As shown in FIG. 2, theelectrode tines 104, when in a retracted state, reside within aninterior 108 of the cannula 102. In the example shown, there are fourtines 104 lying within the interior 108 of the cannula 102 andpositioned for deployment or retraction through four tine exits 106.

The ablation probe 100 further comprises a sheath 110 with tine valves112 that provide for the deployment and retraction of the electrodetines 104. The sheath 110 may be a pliable, malleable covering (e.g.,Fluorinated Ethylene Propylene (FEP), polyester, rubber, plastic,polyvinyl chloride (PVC), or other similar material) that forms an outercoat or layer over cannula 102. In other examples, sheath 110 may beimplemented using a stiff or resistant material. The sheath 110 may beformed onto the surface of the cannula 102 using any suitable technique,such as coating, spraying, electrolysis, etc. In the illustratedembodiments, the tine valves 112 take the form of longitudinal cuts or“slits”, which can open, as illustrated in FIG. 3. Alternatively, thetine valves 112 can also be criss-cross shape, horizontal, or shaped tothe electrode tine geometry and using the cross section of the electrodetine to act as a plug when retracted. In other examples, tine valves 112may be implemented as transverse or angled slits in sheath 110. In theillustrated embodiment, the tine valves 112 are preformed within thesheath 110. That is to say, the tine valves 112 exist prior to theinitial deployment of the electrode tines 104 from the cannula 102.Alternatively, the tine valves 112 may be created within the sheath 110as the deployment of the electrode tines 104 punctures the sheath 110.

When force is applied, the individual tines 104 are pushed through tinevalves 112, which open (or created if not preformed in the sheath 110)in response to the applied pressure of the electrode tines 104 exitingcannula 102, as illustrated in FIG. 4. As the electrode tines 104 aredeployed, the pliable, malleable material used for sheath 110 provides aseal around individual tines 104, preventing, or otherwise minimizing orreducing, any biological material from entering cannula 102 through thecovered tine exits 106 and into the inside of the cannula 102. As a tinearray is retracted, the sides of tine valves 112 contact and provide aseal over tine exits 106. In some examples, sheath 110 may form ahermetic, airtight, non-airtight, full, or partial seal around theelectrode tines 104 as they are deployed or retracted. Thus, it can beappreciated that the tine valves 112 prevent mechanical interferencewith the electrode tine array during either deployment or retraction andreduces the possibility that a tine array may require surgical removalif the electrode tine array is stuck in a deployed or “open” state.

In the embodiment illustrated in FIGS. 1-4, the sheath 110 externallycovers the cannula 102 and tine exits 106. Alternatively, as illustratedin FIG. 5, the sheath 110 may be located inside of the cannula 102,e.g., as an inner coat or layer within the cannula 102. In this case,the tine valves 112 may, in some examples, protrude or extend throughtine exits 106 and cannula 102 as the electrode tines 104 are deployed.Alternatively, a tine valve 112 may not extrude from cannula 116 and,instead, may be forced to one side of a tine exit 106.

In the embodiments illustrated in FIGS. 1-5, the sheath 110 extends theentire length of the cannula 102. Alternatively, as illustrated in FIG.6, the sheath 110 may be configured to cover and overlap the electrodetine exits 106, but not the entire length of cannula 102. In theembodiments illustrated in FIGS. 1-6, the tine valves 112 are alignedaround the longitudinal axis of the cannula 102. Alternatively, the tinevalves 112 may be positioned at offset intervals relative to atransverse axis 114, as illustrated in FIG. 7. In this case, theelectrode tines 104 may be deployed though tine valves 112 at varyingintervals, accommodating tine arrays of varying sizes and positionslying within cannula 102. In other examples, several sets of tine valves112 may be used to accommodate more than one tine array (e.g., a distaland proximal tine arrays).

Although particular embodiments of the present invention have been shownand described, it should be understood that the above discussion is notintended to limit the present invention to these embodiments. It will beobvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present invention. Thus, the present invention is intended to coveralternatives, modifications, and equivalents that may fall within thespirit and scope of the present invention as defined by the claims.

The invention claimed is:
 1. A tissue ablation probe, comprising: anelongated shaft cannula comprising at least one tine exit within a sideof the cannula; at least one electrode tine configured tobe deployed andtracted through the at least one tine exit; a sheath covering the atleast one electrode tine exit, and defining a portion of an exteriorsurface of the cannula, the sheath configured to puncture and open whenthe at least one electrode tine is deployed and to close when the atleast one electrode tine is retracted, wherein the punctured sheathforms a tine valve at each puncture location.
 2. The tissue ablationprobe of claim 1, wherein the at least one electrode tine comprises aplurality of electrode tines.
 3. The tissue ablation probe of claim 1,wherein the sheath comprises a polymer.